We have refined our existing model for myocardial and ventricular mechanics to include the effects of collagen on the elasticity of the myocardium and filling of the left ventricle; wall thickness and curvature effects; pathological fiber organization; myocardial blood flow; myocardial oxygen demand; effects of electrical activation patterns; interaction with the right ventricle; and dynamic vibrations. The model was used in conjunction with ultrasonic kinematic data, gated radionuclide ventriculography, and left-heart catheterization data; and implanted ultrasonic crystals were used to determine performance and contractility parameters. The physiological relationships between phasic coronary arterial, venous, and left ventricular pressure and blood flow were determined during a long diastole and under controlled conditions. A theoretical model was developed and was used to describe contraction of arterioles; it will be used to study mechanisms of hypertension. Theoretical models investigating residual stress in the myocardium and contraction with an ischemic zone are being developed. Congenital heart defects with right ventricular pressure and/or volume overload have been modeled.